The present invention relates to a hinge assembly for rotatably coupling a hinged member to a device housing, and more particularly, to a position holding, viscoelastic dampened, self-latching hinge for holding a hinged member in one of an open position and a closed position relative to a device housing.
In certain hinge applications, it is desirable to provide a hinge which can maintain a hinged member in an open position or a closed position and dampen movement of the hinged member between the open and closed positions at a relatively slow and constant rate. One such application is in the highly competitive field of portable communication devices, (e.g., cellular and PCS phones or light weight covers in automobiles). The fierce competition among portable communication devices has created a premium on improvements to these devices that make them more marketable, with a particular emphasis on styling and aesthetics.
In some devices, a spring bias member is typically installed between the hinged member and the device housing which biases the hinged element to the open position after an initial latching force is manually overcome or after a separate manual latch is released. However, the known hinge assemblies are provided in multiple pieces which are assembled in situ with the hinged member and the device housing. This type of known hinge imparts an axial force on the device housing and the hinged member and is costly to produce. While this additional loading can be accommodated for in the design of certain types of devices which have a sufficient size to provide the necessary load path, in the field of portable communication devices where the trend is to produce smaller and smaller phone devices, the use of this type of hinge assembly can result in premature fatigue and structural failure of the mounting provisions for the hinge in the device housing and/or hinged member. In addition, these known hinge assemblies tend to have an abrupt opening action, effectively slamming the flip half of the phone against the rear stop as the opening motion is completed.
In another known hinge which was designed to address the axial loading problem, a preassembled hinge is provided which can hold a hinged member in an open position or a closed position. The hinge includes an outer shell which reacts to the axial spring load such that no axial force is imparted on the device housing or the hinged member. However, this construction is bulky, and cannot be installed between the device housing and the hinged member with a simple manufacturing operation. Additionally, the hinged member is not held stably in the open position since the closing and opening forces of the hinge are the same. In the open position, the spring force on the hinge which acts to maintain the hinge in the open position is lower than when the hinge is in the closed position and, accordingly, the hinged member is subject to movement or chatter while in the open position. This can cause premature wear of the hinge as well as the device housing and the hinged member which are connected by the hinge. Moreover, movement of the hinged member between the closed and open position in many devices is unregulated, resulting in undesirable residual forces when moved to the open position, as well as premature wear and/or failure of the hinge. This type of hinge also has the slamming problem mentioned in the previous paragraph.
The present invention provides a relatively inexpensive preassembled, self-contained, two position hinge which can hold a hinged member in a first, open position or a second, closed position relative to a device housing without imparting an axial load on the hinged member or the device housing thereby resulting in long operating life and allows the hinged member to move at a relatively constant speed between the open and closed positions. This imparts a sense of high quality and elegance to the motion of the flip half of the phone or automotive cover. The hinge of the present invention can be simply and easily connected to the hinged member and the device housing without tools and with mere finger pressure, thereby yielding reduced assembly cost of the final product.